Studies are proposed to investigate the structure and function of mammalian memory systems. We propose neuropsychological studies of amnesic patients and patients with Parkinson's disease, studies of human eyeblink conditioning, functional magnetic resonance imaging studies, and new studies in the rat, which will complement the studies in humans. The work is organized as five topics.. 1. The organization of declarative memory proposes seven experiments that concern medial temporal lobe function: a) episodic and semantic memory; b) the functions of the perirhinal cortex; c) the problem of task classification; d) the hypothesis that declarative memory is flexible and non-declarative memory, less flexible. 2. Non-declarative memory as an independent entity proposes three experiments concerning a) category (prototype) learning and b) conceptual priming. 3. Eyeblink conditioning proposes four experiments to pursue our finding that awareness of the stimulus contingencies is a prerequisite for differential trace conditioning. We propose to study a) single-cue conditioning; b) the development of awareness during conditioning; c) trace conditioning in amnesia; d) the effects of divided attention on retention of trace conditioning. 4. Declarative and non- declarative memory as revealed in fMRI proposes five experiments using blocked and event-related techniques. We will a) compare perceptual priming and recognition; b) compare priming and recognition in amnesia; and c) study medial temporal lobe activation during retrieval as a function of retention interval. 5. Complementary studies in rats proposes six experiments in our newly operational rat laboratory (up and going since March, 1998. We will assess visual recognition memory following ibotenic or radio-frequency lesions of the hippocampus using a) non- matching to sample; b) the visual paired-comparison task; c) the socially- acquired food preference task . We will also d) determine the locus and size of the effective lesion in the case of task (b) and compare the findings to what has been determined for a spatial task (Moser et al. 1993). Finally 3), we will study the temporal gradient of retrograde amnesia. It is worth noting that a key component of the work in humans is the availability of two profoundly amnesic patients who have no capacity for declarative memory. A second key component of our program is our new work with rats, which is conceptually closely related to our work with humans.